排序方式： 共有6条查询结果，搜索用时 187 毫秒
1
1.
ZHANG Mengshao PANG Yanchun YANG Ben HE Yangjian LIANG Siyu HU Qiang LIN Li 《《地质学报》英文版》2023,97(6):1587-1603
A study of the morphological and microstructural characteristics of helcionelloids from the Nanjiang area (north Sichuan, China) at the northern Yangtze Platform was undertaken, in order to understand their phylogenetic position. Helcionelloids fossils from the Kuanchuanpu Formation of the Changtanhe–Maolinzi section include 7 genera and 11 species. There are distinct differences in the degree of shell bending, the apical morphology and apex position, the outline of the aperture and the height of the shell, all of which constitute important identification features. Although helcionelloid apices exhibit varying degrees of rotation towards the aperture, they do not show any signs of evident distortion. A pair of basally-symmetrical muscle scars are discovered on the shells of helcionelloids (such as Bemella simplex), showing a distinct difference when compared with those of the stem-group gastropod (e.g., Pelagiella). The prismatic shell layer of helcionelloids has been observed, which are common components in Cambrian molluscs, but differ significantly from the dense layer microstructure found in contemporary molluscs. The microstructures, muscle scars and morphological characteristics demonstrate that helcionelloids represent a stem-group of molluscs. 相似文献
2.
对湖北宜昌地区滚子坳剖面寒武系纽芬兰统幸运阶顶底界线的位置进行较为细致的研究.通过切片法及酸蚀法对61个样品进行系统处理,获得了大量的小壳化石、疑源类化石及其他分类位置未定化石.系统鉴定和描述了23属44种.根据具刺疑源类化石Asteridium和小壳化石Protohertzina sp.的首现位置以及无机碳同位素BACE曲线最大负值位置可以推断出埃迪卡拉系-寒武系界线应该位于第1层底部往上约10.5 m处;根据Zhijinites longistriatus的首现位置以及无机碳同位素ZHUCE曲线最大值位置可以推断出幸运阶与第二阶的界线位置大致为第4层底部往上约2.78 m.此外,还将峡东地区的小壳化石Ⅱ带和Ⅲ带重新定义,即将Purella antiqua组合（Zone Ⅱ）修订为Purella antiqua-Siphogonuchites triangularis组合;将Aldanella yanjiahensis组合（Zone Ⅲ）修订为Aldanella yanjiahensis-Zhijiniteslongistriatus组合. 相似文献
3.
本文报道新疆阿克苏地区寒武纪幸运期最早期的小壳化石组合。化石产自玉尔吐斯组底部,包括：Protohertzina anabarica Missarzhevsky, 1973、Protohertzina unguliformis Missarzhevsky, 1973、Anabarites trisulcatus Voronova and Missarzhevsky, 1969、Anabarites ternarius Missarzhevsky in Rozanov et al., 1969、Cambrotubulus decurvatus Missarzhevsky in Rozanov et al., 1969、Olivooides sp.、Kaiyangites novilis Qian and Yin, 1984以及海绵骨针化石。据此可以在新疆阿克苏地区玉尔吐斯组下部建立Anabarites trisulcatus-Protohertzina unguliformis组合带。该组合带下界以Anabarites trisulcatus、Protohertzina ungulifo... 相似文献
4.
LIU Yunhuan ZHANG Yanan SHAO Tiequan TANG Hanhu JIANG Kaituo WANG Qi CHEN Cheng DONG Junyan LIANG Yongchun DAI Jun XUE Jiaqi 《《地质学报》英文版》2016,90(5):1629-1636
Maikhanellids are a distinct group of Cambrian Fortunian small shelly fossils by the cap-shaped profiles and scaly shell ornamentation. According to the individual shell shape and ornamentation feature types of 50 maikhanellids fossils which were collected from Xixiang botia, we confirmed the family Maikhanellidae content of six genera, which are Maikhanella, Ramenta, Purella, Ramentoides, Yunnannopleura and Mediata. Unlike the halkieriid animals whose shells and spicules are articulated on different body parts, maikhanellids were presumably yielded by siphogonuchitid spicules penetrating the intermediate matrix (the "spicule shell" hypothesis), and this is the reason that some researchers treated maikhanellids and co-occurring siphogonuchitids as synonyms. The affinities of Maikhanellids and siphogonuchitids remain debatable. Here, we report three dimensionally phosphatized maikhanellid shells and siphogonuchitid spicule bundles from the Cambrian Fortunian small shell faunas of South China. They differ from all the previously reported maikhanellids and siphogonuchitids, and may represent new types. The intact and smooth surface underneath the partially preserved scales of the shells challenges the "spicule-shell" hypothesis. The present siphogonuchitid spicules differ from the maikhanellid scales in size, morphology, and .arrangement pattern, thus the spicules might not be derived from the shells. Whether the shells and spicule bundles were articulated on different body parts of the same animals remains unknown. 相似文献
5.
6.
ZHANG Ya''nan LIU Yunhuan SHAO Tiequan WANG Qi QIN Jiachen ZHANG Wei LIANG Tanxing 《《地质学报》英文版》2022,96(2):440-446
A new maikhanellid genus, Totornatus gen. nov., from the Lower Cambrian (Fortunian Stage) of Zhangjiagou section at Xixiang County, southern Shaanxi Province, South China, is based on a new taxon T. strigatus gen. et sp. nov. Although showing similar morphology with a cap-shaped shell and an oval aperture to other members of the family, the new species differs from previous maikhanellids in its smooth apex. The apical field consists of dense, small, round or oval granules, which gradually merge to bigger, elongated, scale-like protrusions toward the apertural margin. On this basis, we establish Totornatus strigatus, which shows a transverse groove in two-ninths of its shell. This result enriches the diversity of the earliest mollusks and maikhanellids. 相似文献
1